i'm retired: my day usually starts around 5am, but it's coffee, news, yada yada, and then off to the races: whatever my project is currently (writing/arranging, PA building/maintenance, etc.). i do TB most mornings until the coffee is gone and then again throughout the day (my computer is in my work area) when i can.
when i worked as a 'white-collar professional': 9-9 more or less (lots of downtime, sometimes!)
when i worked in the music biz: all times --- down times were the enemy!
i worked for a large corporation once: 9-5.
entrepreneurialism is difficult to schedule.